Contact screw

ABSTRACT

A contact screw for conductive cores of a shielded cable, said screw being provided to be moved axially in a connecting device by threading; it has a shank with screw threading and a contact tip the section of which provided for penetration of the cable insulation and the shield is provided with a coating of insulating material, the exterior surface of the coating being provided with threading whose pitch is greater than the pitch of the screw threading of the shank.

FIELD OF INVENTION

The present invention relates to a contact screw for conductive cores ofa shielded cable, in particular the data transmission cores of a flatcable having a plurality of conductive cores, such screw being providedto be moved axially by means of threading in a connection device andhaving a shank with screw threading and a contact tip, the section ofthe contact tip provided for penetration of the cable insulation beingprovided with a coating of insulating material.

BACKGROUND OF INVENTION

The problem, particularly in the case of flat cables that have energytransmission and data transmission cores, lies in piercing the dataconductor in the shielded cable without the screw coming in contact withthe shield (electrically conductive material), while in the processachieving good contact resistance between the end of the contact tip andthe conductor and retaining high dielectric strength between shield andconductor.

In the past this object has been attained by means of a contact screwwith an end casing of hard insulating material which extends through thecable jacket, the shield, and the core insulation when the conductor ispierced. One disadvantage of this solution is that the force ofpenetration is transmitted to the insulating material and the shield isdrawn toward the conductor, something which disadvantageously reducesthe distance between shield and conductor.

OBJECTS AND BRIEF DESCRIPTION OF INVENTION

The object of this invention is to eliminate the disadvantages indicatedin the foregoing of a contact screw as defined above.

It is claimed for the invention that this object has been attained for acontact screw of the type indicated by means of the features specifiedin the claims.

In comparison with the state of the art, a higher dielectric strengthbetween shield and conductor is achieved and the force of penetration ofthe metal component of the screw is transmitted by the metal componentrather than by the insulating material. This solution also makes itpossible to achieve a larger contact surface between screw (tip end) andconductor.

Especially advantageous embodiments of the object of the invention arespecified in the dependent claims.

BRIEF DESCRIPTION OF DRAWINGS

The invention is described in somewhat greater detail in what followswith reference to the drawing, in which

FIG. 1 presents a side view of the contact tip end of a contact screwclaimed for the invention;

FIG. 2 is a view similar to that of FIG. 1 with insulating casingmounted;

FIGS. 3 and 4 are diagrams of the mode of operation of contact screws.

DETAILED DESCRIPTION OF THE INVENTION

The drawing (FIGS. 1 and 2) shows the lower part of a contact screw ofmetal with shank 1 and contact tip 2 with mushroom-shaped end 2′. Ascrew threading 3 of predetermined pitch (for example 0.7) is providedon the shank 1. The screw may be moved axially by way of the screwthreading 3 in a tapped hole of a connecting device (not shown).

A casing 4 of insulating material is mounted in the section of screwbetween the end of the shank and the end of the contact tip 2. Thecasing 4 tapers, as does the contact tip 2, to the conical end 2′, beingpositioned between the shoulders 1′ of the end of the shank and 2″ ofthe mushroom-shaped end 2′.

A threading 5, a double helix if desired, the pitch of which is greaterthan that of the screw threading 3 (for example 1.2 mm as opposed to 0.7mm) is provided on the outer surface of the casing 4.

Since the screw threading 3 determines the movement of the screw,relative movement results in the area of the threading 5 of the casing 4which draws the insulation of the conductor upward (that is, away fromthe conductor) and so increases the distance between shield andconductor when the contact screw is screwed in.

The pressure between the flanks of the contact tip 2 of the screw andthe insulating material of the cable is increased and accordingly theelectric strength is further improved by the tapered shape of theinsulating casing 4.

The mushroom-like shape of the end 2′ of the contact tip 2 protects theinsulating casing 4, as a result of which the force of penetration isnow transmitted by the metal component rather than by the insulatingcasing.

FIG. 3 of the drawing presents a purely diagrammatic view of a contactscrew of the state of the art. It is clearly to be seen that the shield10 is pressed closer to the conductor 20 at the point of penetration.

FIG. 4 illustrates the solution claimed for the invention. It is clearlyto be seen how on the insulated casing 4 both the insulation and theshield 10 are at the point of penetration moved away from the conductor20 because the exterior threading 5 is of a pitch greater than that ofthe screw threading 3.

1. A contact screw for conductive cores of a shielded cable comprising ashank with screw threading and a contact tip, wherein a section of thecontact tip provided for penetrating cable insulation has a coating ofinsulating material, and an exterior surface of the coating includesthreading having a pitch which is greater than a pitch of the screwthreading on the shank, wherein the screw is constructed and arranged tomove axially in a connecting device due to said threading on the shank,wherein the contact tip and the coating are configured to taper towardthe end of the screw.
 2. The contact screw as claimed in claim 1,wherein the end of the contact tip is conically-shaped and the coatingis positioned between the shank and a shoulder of said end.
 3. A contactscrew for conductive cores of a shielded cable comprising a shank withscrew threading and a contact tip, wherein a section of the contact tipprovided for penetrating cable insulation has a coating of insulatingmaterial, and an exterior surface of the coating includes threadinghaving a pitch which is greater than a pitch of the screw threading onthe shank, wherein the screw is constructed and arranged to move axiallyin a connecting device due to said threading on the shank, wherein thepitch of the threading on the exterior surface of the coating is atleast twice the pitch of the screw threading on the shank.
 4. Thecontact screw as claimed in claim 3, wherein the end of the contact tipis conically-shaped and the coating is positioned between the shank anda shoulder of said end.